Contactless ignition system for internal combustion engine

ABSTRACT

A contactless ignition system for an internal combustion engine wherein the signal source comprises of a signal generator whose output signal voltage increases in proportion to an increase in the rotation speed of the engine, and the waveform of the output signal from said signal generator is changed by means of a level detector circuit such as a saturation amplifier and a Schmitt circuit for detecting signal levels, whereby any desired advance characteristics are easily attained.

United States Patent Oishi 451 Apr. 4, 1972 [54] CONTACTLESS IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINE [72] Inventor: Kazuo Oishi, Kariya-shi, Japan [73] Assignee: Nippondenso Kabushiki Kaisha [22] Filed: Dec. 15, 1969 [2]] App]. No.: 884,803

[30] Foreign Application Priority Data Dec. 18, 1968 Japan ..43/93368 [52] U.S.Cl ..l23/l48E [51] Int. Cl ..F02p 3/06 [58] Field ofSearch ..l23/l48E [56] References Cited UNITED STATES PATENTS 3,316,448 4/1967 Hardin et al ..l23/l48 E 3,368,539 2/1968 Kidwell ..l23/l48E 3,517,260 6/1970 Oishi....-. ..l23/l48E Primary Examiner-Laurence M. Goodridge Assistant Examiner-Cort Flint AnorneyCushman, Darby 8L Cushman [57] ABSTRACT A contactless ignitionsystem for an internal combustion engine wherein the signal source comprises of a signal generator whose output signal voltage increases in proportion to an increase in the rotation speed of the engine, and the waveform of the output signal from said signal generator is changed by means of a level detector circuit such as a saturation amplifier and a Schmitt circuit for detecting signal levels, whereby any desired advance characteristics are easily attained.

8 Claims, 3 Drawing Figures PATENTEUAPR 4:912 3.653367 INVENTOR BY {@u/WM ATTORNEY 8 CONTACTLESS IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contactless ignition system for use with internal combustion engines and chiefly for use with internal combustion engines for automobiles.

2. Description of the Prior Art With ignition systems of this type which are known to the prior art, the waveform of a signal voltage produced by a signal generator was directly changed to produce an ignition signal and therefore the change of firing position or the fire advance largely depended upon the waveform of the output signal voltages and it was very difficult to obtain any given advance characteristics.

SUMMARY OF THE INVENTION The object of the present invention is therefore to provide a contactless ignition system comprising a signal generator adapted to generate signal voltages in synchronism with the rotation of the engine, the magnitude of said signal voltages being increased in proportion to increase in the rotation speed of the engine, a saturation amplifier adapted to amplify the signal voltage generated by said signal generator and produce a saturated output when said signal voltage exceeds a value determined by the input bias, a regulator for regulating the input bias of said saturation amplifier, an AC coupling circuit for providing an interconnection between said saturation amplifier and a succeeding-stage circuit, and a level detector circuit disposed in said succeeding circuit for signal level detection.

According to the present invention, a remarkable effect is attained in that any desired advance characteristics may easily be obtained by simply regulating the input bias of a saturation amplifier and there is no need to rely on the waveform of signal voltages generated by a signal generator. Moreover, there is a further effect in that a very simple circuit construction may be utilized which employs a saturation amplifier and an AC coupling circuit.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, numeral 1 designates a signal generator which serves as a signal generating device the magnitude of whose output signal voltages increases in proportion to an increase in the rotation speed of the engine. Numeral 2 designates an output winding of the signal generator 1; 3 a generator rotor adapted to rotate in synchronism with the rotation of the engine. Numeral 4 designates an input resistor; 5 a temperature compensating resistor; 6 a temperature compensating diode; 7 an emitter resistor; 8 a transistor; 9 a load resistor; 10 a DC blocking capacitor; 11 a rectifier diode; 12 a rectifier diode; 13 a storage capacitor; 14 a bias resistor; 15 an amplifier-stage input resistor; 16 a temperature compensating diode; 17 a semi-fixed variable resistor for bias regulation; 19 a load resistor; 20 an emitter resistor; 21 a transistor for increasing the degree of amplification for low-speed running; 22 a first-stage amplification transistor; numeral 23 designates a coupling capacitor; 24 a bias resistor; 25 a temperature compensating diode; 26 a temperature compensating resistor; 27 an emitter resistor; 28 a load resistor; 29 a coupling capacitor;

30 a coupling resistor; 31 a second-stage amplification transistor; 32 a bias resistor; 33 a transistor forming a Schmitt circuit; 34 a load resistor; 35 a coupling resistor; 36 a transistor forming a Schmitt circuit; 37 a load resistor; 38 an emitter resistor; 39 a differential capacitor; 40 a differential resistor; 41 a differentiated pulse amplifying transistor; 42 a load resistor; 43 a transistor for a constant voltage circuit; 44 a bias resistor; 45 a Zener diode; 46 a power supply storage battery; 47 a silicon controlled rectifier (hereinafter simply referred to as SCR"); 48 an ignition coil; 49 a primary winding of the ignition coil; 50 a secondary winding of the ignition coil; 51 an ignition plug; 52 a discharge capacitor; 53 a rectifier diode; 54 a high-voltage pulse blocking capacitor; 55 a stepup transformer; 56 a primary winding of the stepup transformer; 57 an output winding of the step-up transfonner; 58 a feedback winding of the step-up transformer; 59 a bias resistor; 60 a resistor for a feedback circuit; 61 a capacitor for the feedback circuit; 62 an oscillating transistor; 63 a bias resistor for the transistor 8.

With the arrangement described above, the operation of the system according to the present invention will be explained. To begin with, a portion of the signal voltages developed across the output winding 2 of the signal generator 1 is delivered as the input signal to the transistor 22 through the resistor 15 and the diode 16. On the other hand, the other portion of the signal voltage is applied through the resistor 4 to the transistor 8 where it is amplified. The signal thus amplified by the transistor 8 is then stored across the capacitor 13 through the diodes 11 and 12. The charge thus stored in the capacitor serves to change the base bias of the transistor 21 and this change in the base bias in turn varies the emitter resistance of the transistor 22. Here, this emitter resistance decreases as the transistor 21 will conduct when the engine rpm is low, whereas said emitter resistance increases as the charging voltage increases in proportion to an increase in the engine rpm thus rendering the transistor 21 nonconductive. In this way, the emitter resistance of the transistor 22 is changed according to the conduction and nonconduction of the transistor 21 and hence the degree of amplification of the amplifier circuit including the transistor 22 is also changed. On the other hand, the base current of the transistor 22 flows through the resistor 17, but the signal current of the signal generator 1 flows only in the direction to cancel this base current. Then, the signal waveform that appears across the load resistor 19 of the transistor 22 is applied through the coupling capacitor 23 to the base of the transistor 31 where it is further amplified and the thus amplified signal waveform is then applied to the Schmitt circuit composed of the transistors 33 and 36. This Schmitt circuit simultaneously serves as a level detector and a rectangular wave shaper and the output rectangular wave of the circuit is differentiated by means of the capacitor 39 and the resistor 40. The differentiated wave is then amplified by the transistor 41 so that a very short pulse-like voltage developed across the resistor 42 is applied to the gate of the SCR 47. This renders the SCR 47 conductive and the discharge capacitor 52 discharges through the primary winding 49 and the anode and cathode of the SCR 47, whereupon a high voltage is generated across the secondary winding 50 of the ignition coil 48 to cause an ignition spark at the ignition plug. On the other hand, the DC-DC converter consisting of the elements ranging from the diode 53 to the transistor 62 inclusive charges the discharge capacitor 52 for the next igniting operation;

Now, the spark-advance principle of the ignition system of the present invention which operates in the mode described above, will be explained in detail hereinafter. The relationship between the signal voltage V of the signal generator 1 and the angular displacement 0 of the engine is as shown in FIG. 2. That is, there is the relation, the signal voltage V =f(n-0), indicating that the signal voltage is a function of the engine rpm n and the angular displacement 0 of the engine. Here, since the signal voltage V is substantially proportional to the engine rpm n at the respective angular displacement, it follows V In FIG. 2, this position takes place at two points and However, since the ignition takes place at the positions on the side of 0, the solution (2) shows a tendency that the value of 0 decreases in proportion to the increase in the number of revolutions. That is, an advance is caused. However, this advance characteristic entirely depends on the characteristic of the signal generator 1 and therefore, as it stands it is difficult to attain various modes of advance characteristic. Thus, according to the present invention, the signal voltage from the signal generator 1 is applied to the saturation amplifier from which it is further applied to the circuit of the succeeding stage through the AC coupling circuit, and a level detecting circuit is provided in this succeeding-stage circuit which determines the ignition trigger level so that any desired advance characteristic may be freely chosen. This will be explained in detail hereunder. In FIG. 1, the waveform developed across the load resistor 19 of the first-stage amplification transistor 22 represents the saturated waveform shown in FIG. 3, and the transistor 22 functions as a saturation amplifier so that if an AC coupling is established between this transistor and the second-stage amplification transistor 31 by means of the capacitor 23, it results in the following. That is, if it is chosen such that the center level of the signal waveform prior to the saturation is given by Vt=nf(6) the level after the saturation may be obtained as 1 21r "@it? (where h(0) represents the waveform developed following the AC coupling), and therefore the following relationships are established between g(6) and h(0) e at A That is, the adjustment of the zero level takes place by virtue of the saturation of the waveform. Accordingly, the new trigger position is moved to a position which is lower by A as compared with that before the saturation. In comparison with the initial level, this represents a drop of (V, A) volts. In terms of the ignition points (of course, the trigger level here is so chosen that it is lower than the saturated voltage), the following change takes place Before saturation 0,, =f( V,)

After saturation 0', =f'( V, A)

Here, the value of A may be freely changed by adjusting the bias of the first-stage amplification transistor 22 consistituting the saturation amplifier. In addition, if the signal generator 1 increases the amplitude of the generated signal voltages in proportion to an increase in the number of revolutions, the value of A may vary correspondingly. In this manner, with a mere adjustment of the bias-regulating variable resistor 17 of 75 claim 3,

the first-stage amplification transistor 22 in the circuitry of the ignition system according to the present invention, the advance characteristics due to fluctuations in the properties of the circuit components such as transistors and resistors may be corrected, and moreover any desired advance characteristics may be positively attained through the adjustment of the variable resistor 17.

I claim:

l. A contactless ignition system for an internal combustion engine, said ignition system comprising:

a signal generator means for producing a signal voltage in synchronism with the rotation of the engine, the magnitude of said signal voltage increasing in accordance with increasing rotational speed of the engine,

a saturation'amplifier means with its input effectively connected to said signal generator means for producing an amplified output signal which becomes saturated when said signal voltage reaches a predetermined level,

a level regulator means for controlling an input bias to said amplifier,

an amplification regulator means for controlling the amplification factor of said saturation amplifier means thereby controlling the time period during which said output signal is saturated, and

an AC coupling circuit for connecting the AC components of the amplified output signal of said saturation amplifier as an input AC signal to a succeeding circuit said succeeding circuit including a level detecting circuit for producing an ignition signal by detecting a predetermined level of said input AC signal applied to said succeeding circuit through said AC coupling circuit whereby the effective advance of said ignition signal is determined by the period during which said output signal from said saturation amplifier is saturated.

2. A contactless ignition system according to claim 1, further comprising means for supplying said amplification regulator means with said signal voltage from said signal generator means and for producing a control signal corresponding to a desired ignition advance angle with the amplification factor of said saturation amplifier means being controlled by said control signal produced by said amplification regulator means.

3. A system for automatically advancing an ignition angle in an internal combustion engine, said system comprising:

a signal generator means for producing a signal voltage in synchronism with the rotation of the engine, the magnitude of said signal voltage increasing in accordance with increasing rotational speed of the engine,

a saturation amplifier means with its input effectively connected to said signal generator means for producing an amplified output signal,

a level regulator means for controlling an input bias to said saturation amplifier,

an amplification regulator means for controlling the amplification factor of said saturation amplifier,

said amplified output signal being asymmetrically saturated when the rotational speed of the engine reaches a value determined by said input bias and by said amplification factor,

a succeeding circuit including a level detecting circuit and,

means for supplying an input of said succeeding circuit with said asymmetrically saturated signal through an AC coupling circuit for producing an ignition signal having a desired advance angle determined by the degree of asymmetric saturation of said amplified output signal.

4. A system for automatically advancing an ignition angle as in claim 3, wherein:

said saturation amplifier means has an amplification factor which is of a relatively high value when the engine rotation is lower than a predetermined value and which is then controllably decreased in accordance with increasing engine rotational speeds.

5. A system automatically advancing an ignition angle as in wherein:

said saturation amplifier means comprises:

a first transistor having an emitter, collector and base an output resistance connected between the collector of said first transistor and a power terminal which is connectable to a power source,

an emitter resistance connected between the emitter of said first transistor and a ground potential terminal, and

a variable resistance connected between the base of said first transistor and said power terminal and wherein:

said amplification regulator means comprises:

' a series electrical circuit of a second transistor having an emitter, collector and base, and v a resistor connected in series with the emitter-collector of said second transistor, said series circuit being connected in parallel with said emitter resistance.

6. An improvement for an internal combustion engine automatic ignition advance system of the type that utilizes a level detector to determine ignition timing by detecting when an input AC signal in synchronism with engine rotation exceeds a preset trigger level where the input AC signal is normally taken directly or after linear amplification as a signal voltage from a signal generator operated in synchronism with the engine and producing higher signal voltages as the engine speed is increased, said improvement comprising:

a saturation amplifier means with an input efi'ectively electrically connected to an output of said signal generator for producing a saturated output signal which is saturated for at least part of each cycle of an AC signal output from said signal generator after the engine rotational speed exceeds a predetermined value and which becomes increasingly saturated as higher voltages are applied to its input in response to higher engine rotational speeds,

an AC coupling means connected between an output of said saturation amplifier means and an input of said level detector for passing the AC component only of said saturated output signal to the level detector whereby the effective magnitude of ignition advance is determined by the degree of saturation of said saturation amplifier means, and

means for controlling the degree of saturation of said saturation amplifier means.

7. An improvement as in claim 6 wherein said means for controlling comprises:

an amplification regulator means effectively connected to said signal generator and to said saturation amplifier means for controlling the amplification factor of said saturation amplifier means in accordance with the output from said signal generator to cause the amplification factor, and hence the degree of saturation, to decrease with increasing engine rotational speeds thereby resulting in lesser ignition advance angles at higher engine speeds.

8. An improvement as in claim 7 wherein said saturation amplifier means comprises a transistor amplifier including controlled bias means for determining the predetermined value of engine rotational speed beyond which the output of said transistor amplifier is saturated. 

1. A contactless ignition system for an internal combustion engine, said ignition system comprising: a signal generator means for producing a signal voltage in synchronism with the rotation of the engine, the magnitude of said signal voltage increasing in accordance with increasing rotational speed of the engine, a saturation amplifier means with its input effectively connected to said signal generator means for producing an amplified output signal which becomes saturated when said signal voltage reaches a predetermined level, a level regulator means for controlling an input bias to said amplifier, an amplification regulator means for controlling the amplification factor of said saturation amplifier means thereby controlling the time period during which said output signal is saturated, and an AC coupling circuit for connecting the AC components of the amplified output signal of said saturation amplifier as an input AC signal to a succeeding circuit said succeeding circuit including a level detecting circuit for producing an ignition signal by detecting a predetermined level of said input AC signal applied to said succeeding circuit through said AC coupling circuit whereby the effective advance of said ignition signal is determined by the period during which said output signal from said saturation amplifier is saturated.
 2. A contactless ignition system according to claim 1, further comprising means for supplying said amplification regulator means with said signal voltage from said signal generator means and for producing a control signal corresponding to a desired ignition advance angle with the amplification factor of said saturation amplifier means being controlled by said control signal produced by said amplification regulator means.
 3. A system for automatically advancing an ignition angle in an internal combustion engine, said system comprising: a signal generator means for producing a signal voltage in synchronism with the rotation of the engine, the magnitude of said signal voltage increasing in accordance with increasing rotational speed of the engine, a saturation amplifier means with its input effectively connected to said signal generator means for producing an amplified output signal, a level regulator means for controlling an input bias to said saturation amplifier, an amplification regulator means for controlling the amplification factor of said saturation amplifier, said amplified output signal being asymmetrically saturated when the rotational speed of the engine reaches a value determined by said input bias and by said amplification factor, a succeeding circuit including a level detecting circuit and, means for supplying an input oF said succeeding circuit with said asymmetrically saturated signal through an AC coupling circuit for producing an ignition signal having a desired advance angle determined by the degree of asymmetric saturation of said amplified output signal.
 4. A system for automatically advancing an ignition angle as in claim 3, wherein: said saturation amplifier means has an amplification factor which is of a relatively high value when the engine rotation is lower than a predetermined value and which is then controllably decreased in accordance with increasing engine rotational speeds.
 5. A system automatically advancing an ignition angle as in claim 3, wherein: said saturation amplifier means comprises: a first transistor having an emitter, collector and base an output resistance connected between the collector of said first transistor and a power terminal which is connectable to a power source, an emitter resistance connected between the emitter of said first transistor and a ground potential terminal, and a variable resistance connected between the base of said first transistor and said power terminal and wherein: said amplification regulator means comprises: a series electrical circuit of a second transistor having an emitter, collector and base, and a resistor connected in series with the emitter-collector of said second transistor, said series circuit being connected in parallel with said emitter resistance.
 6. An improvement for an internal combustion engine automatic ignition advance system of the type that utilizes a level detector to determine ignition timing by detecting when an input AC signal in synchronism with engine rotation exceeds a preset trigger level where the input AC signal is normally taken directly or after linear amplification as a signal voltage from a signal generator operated in synchronism with the engine and producing higher signal voltages as the engine speed is increased, said improvement comprising: a saturation amplifier means with an input effectively electrically connected to an output of said signal generator for producing a saturated output signal which is saturated for at least part of each cycle of an AC signal output from said signal generator after the engine rotational speed exceeds a predetermined value and which becomes increasingly saturated as higher voltages are applied to its input in response to higher engine rotational speeds, an AC coupling means connected between an output of said saturation amplifier means and an input of said level detector for passing the AC component only of said saturated output signal to the level detector whereby the effective magnitude of ignition advance is determined by the degree of saturation of said saturation amplifier means, and means for controlling the degree of saturation of said saturation amplifier means.
 7. An improvement as in claim 6 wherein said means for controlling comprises: an amplification regulator means effectively connected to said signal generator and to said saturation amplifier means for controlling the amplification factor of said saturation amplifier means in accordance with the output from said signal generator to cause the amplification factor, and hence the degree of saturation, to decrease with increasing engine rotational speeds thereby resulting in lesser ignition advance angles at higher engine speeds.
 8. An improvement as in claim 7 wherein said saturation amplifier means comprises a transistor amplifier including controlled bias means for determining the predetermined value of engine rotational speed beyond which the output of said transistor amplifier is saturated. 